Cardiac muscle cells are incapable of growth and differentiation by themselves. Therefore, when the cardiac muscle cells are damaged, they cannot be regenerated and, hence, dysfunction (heart failure) may be induced. To cure this diseased state, replacement type therapies such as heart transplantation, use of an artificial (mechanical) heart, etc. have been employed. However, heart transplantation is problematic due to an insufficient number of donors. The use of an artificial heart suffers from the disadvantage that quality of life is lowered.
Three techniques composed of cell transplantation, alleviation of ventricular load by use of a ventricular assist system, and hemocathasis by plasmapheresis are considered effective for achieving regeneration of cardiac muscles. Here, hemocathasis by plasmapheresis is a technique for cleaning the blood serving as a culture medium and for permitting the cells to function more easily; therefore, the former two techniques alone may be sufficient to obtain the desired effect. Where this therapy is performed, the ventricular assist system is removed when it is confirmed that the cardiac muscles have sufficiently been regenerated and the functions of the patient's own heart have restored.
As for the cell transplantation, among the above-mentioned techniques, there are a number of methods. An example of one method involves sampling bone marrow from the hipbone, separating the marrow cells, and injecting the marrow cells through a catheter into a coronary bypass formed at the time of a surgical operation of embedding the ventricular assist system. In another example, thoracotomy is again performed after the ventricular assist system embedding operation, and myoblast and marrow cells are supplied by injection into a multiplicity of portions (for example, 60 portions) of the wall of the heart.
The first method mentioned by way of example has merit in that it is less invasive due to the absence of thoracotomy. However, it is difficult to concentrate the cells into the region of myocardiac infarction. On the other hand, in the latter method mentioned above, injection of the cells is performed by way of thoracotomy, so that the growth factor secreted after injection into comparatively remote portions of the wall of the heart infiltrates into the infarct portion, which is effective. Even in the latter method, however, the cells are not sufficiently concentrated into the infarction portion. Besides, the latter method has the disadvantage of being heavily invasive, since it requires thoracotomy.
If the injection of the cells can be carried out at the time of embedding the ventricular assist system, the cells can be injected directly into the infarct portion. However, injecting the cells simultaneously while embedding the ventricular assist system is difficult to achieve, since the culture of cells takes a few weeks, and, in practice, the ventricular assist system must often be embedded with unexpected timing. Chisato Nojiri, Journal of Japan Surgical Society, Vol. 103, No. 9, pp. 607-610, 2002 contains a description of a ventricular assist system which includes a magnetic levitation type pump.